Telephone-exchange system.



G. E. HAGUE.

TELEPHONE EXCHANGE SYSTEM.

APPLIUATION FILED APR. 24, 1907.

966,013. Patented Aug. 2, 1910.

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Patented Aug. 2, 1910.

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UNITE STATS PATENT OFFICE;

CHARLES E. HAGUE, OF ROCHESTER, NEW YORK, ASSIGNOR T0 STROMBERG-CARLSON'TELEPHONE MANUFACTURING COMPANY, OF ROCHESTER, NEW YORK, A CORPORA- TIONOF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

seems.

To all whom it may concern:

Be it known that 1, CHARLES E. HAGUE, a citizen of the United States,residing at Rochester, in the county of Monroe and State of New York,have invented a certain new and useful Improvement in Telephone-Exchange Systems, of which the following is a full, clear, concise, andexact description, reference being had to the accompanying drawings,forming a part of this specification.

My invention relates to telephone exchange systems and particularly tothe central exchange arrangement of trunk line systems, and its objectis to provide means whereby the local exchange operator making use ofthe trunk line may control the application of ringing current to thecalled subscriber connected with the main exchange.

My improved arrangement is particularly adaptable when used inconnection with antomatic ringing systems, and the trunk operatorascertaining the required connection sets the corresponding selectivekey whereafter the application of the corresponding ringing current tothe subscribers line is controlled by the local exchange operator.

The details of my invention will be best understood by reference to theaccompanying drawing, wherein Figure 1 diagrannnatically shows a trunkcircuit arrangement at the main exchange and the operators cord circuitarrangement at the local exchange, and also the connection of theautomatic selective ringing mechanism with the trunk circuit, and Fig. 2shows the mechanical connection between the several selective ringingkeys and the armature of the relay used to retain any of such keys inoperated position until the called subscriber responds.

Substation A as shown in Fig. 1 is of the local battery type providedwith the ordinary telephonic apparatus comprising switch hook 1,receiver 2, transmitter 3, battery at,

signal bell 5 and the calling generator 6 connected 1n brldge of the huelimbs a, b, the

' line limbs terminating normally at the exchange in the springjack sand the line indicator 7. The cord circuit at the local exchange Lterminates in plugs 8 and 9, tip and sleeve contacts of the plug 8 beingconnected through tip and sleeve strands 10 and 11, respectively, withthe operators side of the operators key K, while the tip and sleeveSpecification of Letters Patent.

Application filed April 24, 1907.

Patented Aug. 2, 1910.

Serial No. 369,986.

contacts of the plug 9 connect through cord strands 12 and 13,respectively, with the ringing side of the operators key K. Actuationofthe operators side of the key will connect the operators talking set 0in bridge of the cord strands, and actuation of the ringing side of thekey will connect the generator G in bridge of the cord strands 12 and13. Auxiliary contacts 14 and 15 are provided, respectively, for theplugs 8 and 9, both connected through conductor 16 with ground E. Asupervisory relay 17 is connected in bridge of the strands 12 and 13 andcontrols a local supervisory circuit comprising the battery 18 andsupervisory lamp 19.

The substation B connected with the main exchange is of the commonbattery type provided with the receiver hook 1, receiver 2, transmitter3 and signal bell 5, the signal bell being bridged across the line inseries with a condenser 20, the substation being normally connectedthrough party line limbs a, b with the terminals of the common battery21 and including the wind ings of a line relay 22 and the a "matures 23and 2 1 of the cut oil relay 25. The line relay controls the localcircuit for the indicating lamp 26. Three other party substations B 13*,B are shown also connected across the line limbs a, Z) and are providedwith similar apparatus as that shown at the substation B.

The trunk cord circuit T terminates at one end in a plug 27 forconnection with the multiple jacks 2S and 29 connected with thesubstation B and at its other end terminates in a jack 30 for connectionwith the plug 9 at the local exchange. The trunk cord circuit is dividedinto two conductively separated, but inductively associated, sections TT, the tip and sleeve contacts of the springjack 30 being connectedthrough the windings 31 and 32 of the repeating coils 33 and 3et,respectively, a condenser 35 being connected between these windings. Thetip and sleeve contacts of the plug 27 are adapted for connectionthrough the windings 36 and 37 of the repeating coils, a condenser 38being included between these windings. The continuity of the sleevestrand of the section T is normally discontinuous at the contact 39 andarmature 40 of the relay 41, and the tip strand of this section isnormally discontinuous at the contact 42 and a second armature 43 ofthis relay, this tip strand being normally also discontinuous at thearmature 44 and contact 45 for the relay 46. The winding 47 of the relay48 is in series with the condenser 49 in a circuit bridged across thestrands of the section T. The armature 50 for this relay normallyengages the back contact 51 connected with one terminal of the relay 41.The armature 52 of the relay 46 controls the current supply to the trunkcircuit supervisory lamp 53. The automatic ringing arrangement is shownat the top of the drawing and the mechanical arrangement and relationsof the parts thereof may be as described below. This ringing mechanismis provided with a plu rality of selective keys 54 54 54 and 54*. Theactuating springs 55 55 55 and 55* of these keys are connected togetherand with the armature 56 of the locking relay 57, while the actuatingsprings 57 57 57 and 57 of the keys are connected together and with thearmature 58 of the relay 57 through the condenser 59. A common conductor60 connects with one terminal of the ringing current source 61 61 61 and61 and with the contacts 62 62 62 and 62*, associated with the switchsprings 55 55 55 and 55, respectively. The current interrupters 63 63 63and 63 are associated with the re spective keys, each comprising twoconductors 64 and 65 and a middle ring composed of segments 66 and 67,the segment 67 of each interrupter being connected with the ring 65thereof and with the contact 68 of the respective key. The segment 66 ofeach interrupter is connected with the ring 64 thereof and with a commonconductor 69 connecting with a second armature 70 controlled by therelay 57 and with the contact 71 for the armature 52 of the relay 46.The other terminal of each of the generators 61 61 61 and 61 connectswith the ring 65 of the corresponding interrupter, and upon actuation ofa selective key the corresponding generator will be connected throughthe key with the armatures 56 and 58 of the relay 57, the alternatecontacts 72 and 73 of the armatures 58 and 56, respectively, beingconnected with the alternate contacts 74 and 75, respectively, of therelay 41.

A controlling relay 76 is bridged about the condenser 59, and controlsan armature 77 whose contact 78 is connected with one terminal of anauxiliary winding 79 for the relay 48, the other terminal of thiswinding connecting with the front contact 80 for the armature 50.

Let us suppose that the subscriber at substation A desires connectionwith the subscriber at party substation B. Subscriber at substation Aupon actuation of the generator 6 causes actuation of the indicator 7 atthe local exchange, and the local operator upon insertion of the plug 8into the jack 8 actuates her key to connect her talking set 0 so she mayascertain the connection desired. This desired connection iscommunicated to the trunk operator through order circuits in the wellknown way, but which circuits are here not shown, forming no part ofthis invention. The trunk operator immediately inserts the calling plug27 into one of the multiple acks 28 and 29 and sets the selective key 54connected with the generator 61 whose current is of such character as toactuate only the signal bell at substation B upon being sent into theline, and the trunk operator also notifies the local operator whichtrunk line she is to use. Upon insertion of the plug 27 in thespringjack circuit is closed from the negative side of battery 21,through conductor 81, through relay 46 to the sleeve strand and contactof plug 27, through conductor 82 connecting together the ack thimbles83, through cut-01f relay 25 to the positive side of battery 21. Thiscauses energization of relays 25 and 46, relay 25 upon attraction of itsarmatures 23 and 24 serving to disconnect the line relay 22 and linelamp 26 from service, and relay 46 serving to attract the armature 44 tocontact 45 and the armature 52 to contact 71, and this last connectioncloses a circuit extending from the positive side of battery 21 to thearmature 52 through contact 71, to conductor 84, to armature 70 andcontact 85 through supervisory lamp 53 and through conductor 86 back tothe negative side of battery 21, the lamp 53 being thus illuminated.Upon connection of the plug 9 with the springjack 30 by the localexchange operator another circuit is closed as follows: From thenegative side of battery 21 through conductor 81, through relay 41,through conductor 87, through contact 51 and armature 50 to conductor88, to thimble 89 of springjack 30, through auxiliary con tact 15,through conductor 16 to ground E and thence to the grounded positiveside of battery 21. Relay 41 becoming energized draws its armatures 40and 43 into engagement with the contacts 42 and 39, respectively, tomake continuous the cord strands of the section T. Upon connection ofthe plug 9 with the jack 30 circuit is also closed as follows: From thenegative side of battery 21, through conductor 81, through relay 57,through conductor 88, through t-himble 89 and contact 15 to ground E andto the grounded side of battery 21. Relay 57 thus energized draws itsarmatures into engagement with contacts 72 and 73 to extend the ringingcurrent from the generator 61 to the contacts 74 and 75 which are atthis stage disconnected from the amnatures 40 and 43. Everything is inreadiness now for the application of the selective ringing current tothe party line leading to substation B and the local exchange operatoractuates her ringing key to connect the generator G across the cordstrands 12 and 13 whereby alternating current is sent through thespringjack 30 and winding 47 of the relay 48 bridged across the cordstrands of the section T. The relay 48 becoming energized attracts itsarmature away from the contact 51 and into engagement with the contact80 thereby closing circuit through winding 79 as follows: Negative sideof battery 21, through conductor 81, through armature 77, contact 78,through winding 79, contact 80 and armature 50, conductor 88, thimble89, contact 15 and conductor 16 to ground E and from there to thegrounded'side of battery 21, this local circuit maintaining energizationof the relay 48 upon release of the ringing key by the operator at thelocal eX- change, and this local circuit being once closed the controlof the ringing current is beyond the local exchange operator.

The circuit through the relay 41 passes through the contact 51 andarmature 50, but upon attraction of this armature the relay becomesdeenergized and its armatures 43 and 40 again connect with the livecontacts 74 and 75 connected with the generator 61 and this selectivecurrent immediately flows through the line limbs a, Z) and through thesignal bell 5 at the substation B to signal the subscriber, and thiscurrent continues until the subscriber answers, being interruptedregularly, of course, upon disconnection of the contact 68 from the livecontact 67. The subscriber at substation B, on receiving a signal,removes his receiver from the hook thereby closing the followingcircuit: From the negative side of battery 21, conductor 81, relay 4G,sleeve contact of springjack 27, sleeve contact of springjack 28, linelimb a, through the substation receiver and transmitter through linelimb 5, through the tip contact of springjack 28, tip contact of plug27, armature 44 and contact 45 of relay 46 to armature 43, throughconductor 90, contact 72 and armature 58 of relay 57, through the relay7 6 to key spring 57, contact 68, through segment 66 of the interrupter63, to ring 64, to conductor (39, conductor 84, contact 71 and. armature52 of relay 46 and through conductor 93 to the positive side of battery21. Relay 7 (3 is adjusted to be unresponsive to alternating current,and will, therefore, not be actuated by the signaling current from thegenerator 61 and the condenser 59 is interposed in the ringing circuitto allow passage of alternating current through the ringing circuit butto deflect the direct cur rent through the relay 76. Relay 76 thenbecoming energized, its armature 77 breaks connection with contact 78,thereby opening the local circuit through winding 79 of the relay 48 andthe armature 50 upon release again engages contact 51 to reclose thecircuit through the relay 41, and the armatures 40 and 43 of said relaybecoming attracted to the contacts 39 and 42 cause the cord strands tobecome continuous and the connected subscribers are connected fortelephonic conversation.

When the local exchange operator connected with the springjack 30 andbefore substation B was signaled, the supervisory relay 17 was connectedin bridge of the bat tery 21 through the following circuit: Fromnegative side of battery 21 to the armature 94 of the relay 95, throughcontact 96 to the inner terminal of repeating winding 32 through saidwinding, through the sleeve strand and sleeve spring of springjack 30,through the sleeve contact of plug 9 and sleeve strand 13, through relay17, through tip strand 12 and tip of plug 9, through tip spring and tipstrand of the jack 30, through repeating winding 31, through conductor96, through contact 97 of armature 98 of relay 95 and to positive sideof battery 21, thus causing the illumination of the lamp 19 controlledby the relay 17. Upon answering of the subscriber at substation B inresponse to the calling signals, a circuit is traced as follows: Fromthe negative side of battery 21, conductor 81, relay 46, sleeve strandand contact of plug 27, sleeve spring of jack 28, through line limb a,through the substation B to line limb Z) to tip spring of jack 28, tipcontact and strand of plug 27, through armature 43 and contact 42 ofrelay 41, through conductor 99, through relay 95 and to positive side ofbattery 21. Relay 95 thus becomes energized to attract its armatures tobreak the battery connection with the supervisory relay 17 which becomesdeenergized to cause opening of the supervisory lamp circuit and thelocal exchange operator is notified that the called subscriber hasanswered. After conversation is completed between the connected parties,subscriber at substation B hangs up his receiver and thereby opens thecircuit, thus traced, with the result that relay 95 becomes deenergizedto reconnect the battery with the supervisory relay 17 to again causeillu mination of the supervisory lamp 19, and the operator receivingthis signal withdraws the plu 9 from the jack 30. ithdrawal of thisplug, however, breaks the circuit through the relay 57, and the armature70 of said relay being released to reengage the contact 85 again causesclosure of the circuit through the supervisory lamp 53 for the trunkoperator, thus notifying this operator that conversation isOOITlPlQ-tt-Ed, and she withdraws the plug 27 from the connected line.

As shown in Fig. 2, the keys 55 55 55 and 55 may be provided withlocking mechanism also mechanically associated with the &

relay 57, so that upon actuation of this relay 57 upon connection ofplug 9 with the springjack 30, the depressed key 55 would be locked inits depressed position until deenergization of said relay upondisconnection of the plug 9, whereupon the depressed key would becomereleased at the same time that the supervisory signal 53 would becomeilluminated at the close of conversation between the connected parties.After the local exchange operator disconnects the cord circuit from thespringjack s the cord circuits and selective signaling apparatus areagain in normal condition ready for another connection.

It will be noticed that ring (34 of each interrupter is connected toground when the plug 27 is inserted in a springjack, and through thefollowing circuit: rings 64, conductors 69 and 84, contact 71 andarmature 52 of relay 46 and conductor 93 to ground, thus before thesubscriber on the party line answers there will be alternate pulsationsof ringing current and ground applied to the line as the groundedsegment 66 or the ring ing current segment (57 becomes connected withcontact 68 of the ringing key actuated. The line is, therefore, relievedof static charges after each application of ringing current, and is alsorelieved of such static charges when the subscriber unhangs hisreceiver, as the circuit through relay 76 must include the groundedsegments 66 and 64: of the interrupter, and before alternating currentcan again be applied to the line, relay 41 will have become deenergizedto with draw the cord strands from the ringing current contacts 7 l and75, and when conversation then takes place there will be no interferencefrom static or other disturbing influences.

By means of my invention a trunk operator, as before described, needonly apply the trunk circuit to the line to be called, to notify thecalling operator of the trunk to be used and to set the proper selectivekey, and thereafter need pay no attention to the connections until shereceives the supervisory signals that conversation is completed, whenshe need only withdraw the plug 27 from the jack. After the trunkoperator has established the necessary conditions for calling therequired substation, the application of ringing current is controlled bythe local ex change operator, but this control is only temporary, asconnection of the generator Gr serves merely to initially energize relay4S, whereupon the local energizing circuit therefor maintainsenergization thereof and ringing current is applied, in the manner asbefore described, to the called line, these con nections being performedentirely automatically, and the local exchange operator is advised byher supervisory lamp 19 of the conditions at the trunk station and ofthe called substation line. By virtue of this arrange ment, therefor, itis necessary only to establish the necessary conditions whereafter theactual calling of the subscriber and all of the supervisory andcontrolling steps are performed entirely automatically, thus relievingboth the trunk and local operator of unnecessary work. At the same timethe circuit arrangements are very simple and eflicient. I do not wish,however, to be limited to the arrangement as shown, as changes mayreadily be made therein without departing from the scope of myinvention, but

I claim as new and desire to secure by Letters Patent:

1. In a telephone exchange system, the combination with a centralexchange, of telephone lines leading therefrom and terminating insubstations, a cord circuit at the central exchange, ,a trunk circuitleading from the central exchange, a source of ringing currentassociated with the trunk circuit, a relay controlling the connection ofsaid source of ringing current with the trunk line, means uponconnection of the cord circuit with the trunk circuit for closingcircuit through said relay to disconnect the source of ringing currentfrom the trunk circuit, a second relay controlling the circuit throughsaid first relay, and source of current associated with the cordcircuit, connection of said source of current with the cord circuit whenthe cord circuit is connect ed with the trunk line causing actuation ofsaid second relay to open the circuit through the first relay wherebythe source of ringing current will be connected with the trunk circuit.

2. In a telephone exchange system, the combination with an operatorscord circuit at a central exchange, of a trunk line for connecting saidexchange with a main exchange, a source of ringing current associatedwith the trunk circuit, a relay normally disposed to open the circuitfrom said ringing source, a second relay normally disposed to close theringing circuit at another point, energizing circuits closed throughsaid relays upon connection of the cord circuit with the trunk circuitwhereby the first relay becomes energized to close the break in theringing circuit and said second relay becomes energized to open theringing circuit, a third relay controlling the circuit through saidsecond relay, and a source of current associated with the cord circuit,connection of said source with the cord circuit causing current flowthrough said trunk line and third relay whereby said second relaycircuit is opened and the ringing circuit again closed.

3. In a telephone exchange system, the combination with a centralexchange, of substations connected therewith through telephone lines, acord circuit at the central exchange for connectin with said lines, atrunk clrcuit leading from said exchange to a main exchange forconnection at said main exchange with telephone lines leading tosubstations to be called, a source of ringing current at the mainstation associated with the trunk circuit, a relay controlling the continuity of the circuit from said source of ringing current to the trunkcircuit, a second relay controlling the connection of the ringingcircuit with the trunk circuit, energizing circuits for said relaysclosed upon connection of the cord circuit with the trunk circuit at thecentral exchange to cause the first relay to continue the ringingcircuit to the cord circuit and said second relay to disconnect theringing circuit from the trunk circuit, a third relay controlling thecircuit through said second relay, a source of current associated withthe cord circuit, connection of said source with the cord circuit andconnected trunk line causing current flow through said third relay toopen the circuit through the second relay whereby the source of ringingcurrent is connected with the trunk circuit and with the line connectedtherewith to actuate substation apparatus, and means for again closingcircuit through said second relay to disconnect the ringing source uponactuation of substation apparatus in response to the signaling current.

4. In a telephone exchange system, the combination with a centralexchange, of substations connccted therewith through telephone lines, acord circuit at the central exchange for connecting with said lines, atrunk circuit leading from said exchange to a main exchange forconnection at said main exchange with telephone lines leading tosubstations to be called, a source of ringing current at the mainstation associated with the trunk circuit, a relay controlling thecontinuity of the circuit from said source of ringing current to thetrunk circuit, a second relay controlling the connection of the ringingcircuit with the trunk circuit, energizing circuits for said relaysclosed upon connection of the cord cir uit with the trunk circuit at thecentral exchange to cause the first relay to continue the ringingcircuit to the cord circuit and said second relay to disconnect theringing circuit from the trunk circuit, a third relay controlling thecircuit through said second relay, a source of cur rent associated withthe cord circuit, connection of said source with the cord circuit andconnected trunk line causing current flow through said third relay toopen the circuit through the second relay whereby the source of ringingcurrent is connected with the trunk circuit and with the line connectedtherewith to actuate substation apparatus, and a fourth relay having acircuit controlled by apparatus at the called substation and adaptedupon actuation of substation apparatus to again cause closure of thecircuit through the second relay whereby said source of ringing currentis disconnected from the trunk circuit.

5. In a telephone exchange system, the combination with a centralexchange, of substations connected therewith through telephone lines, acord circuit at the central exchange for connecting with said lines, atrunk circuit leading from said exchange to a main exchange forconnection at-said main exchange with telephone lines leading tosubstations to be called, a source of ringing current at the mainstation associated with the trunk circuit, a relay controlling thecontinuity of the circuit from said source of ringing current to thetrunk circuit, a second relay controlling the connection of the ringingcircuit with the trunk circuit, energizing circuits for said relaysclosed upon connection of the cord circuit with the trunk circuit at thecentral exchange to cause the first relay to continue the ringingcircuit to the cord circuit and said second relay to disconnect theringing circuit from the trunk circuit, a third relay controlling thecircuit through said second relay, a source of current associated withthe cord circuit, connection of said source with the cord circuit andconnected trunk line causing current flow through said third relay toopen the circuit through the second relay whereby the source of ringingcurrent is connected with the trunk circuit and with the line connectedtherewith to actuate substation apparatus, a fourth relay, a localenergizing circuit for said third relay controlled by said fourth relayto maintain energization of the third relay upon disconnection of thesource of current from the cord circuit, and a circuit for said fourthrelay controlled by apparatus at the called substation, actuation ofsaid apparatus causing said fourth relay to be actuated to break thelocal energizing circuit whereby said second relay is again included incircuit and energized to disconnect 'the main circuit from the trunkline.

6. In a telephone exchange system, the combination with a trunk circuitat a main exchange adapted for connection with lines leading tosubstations to be called, of a cord circuit at a subexchange forconnecting said trunk line with lines leading to calling substations, asource of ringing current at the main exchange, means controlled by thesubexchange operator and operable independently of the connection of thetrunk circuit with the line, for primarily establishing connectionbetween the source of ringing current and the trunk line whereby ringingcurrent passes through the connected telephone line to the substation tobe called, automatic means for maintaining the flow of calling currentto the called substation,

and means controlled by apparatus at the called substation for causingdisconnection of the ringing circuit.

7 In a telephone exchange system, the combination with a trunk line forconnection with telephone lines leading to substations to be called, ofa cord circuit for connecting said trunk line with telephone linesleading to calling substations, a source of ringing current associatedwith the trunk circuit, electromagnetic mechanism actuated uponconnection of the cord circuit with the trunk line to continue thecircuit from the ringing source to the trunk circuit, a second electro-I magnetic mechanism controlling the connection of said ringing circuitwith the trunk circuit and actuated upon connection of the cord circuitwith the trunk line to disconnect the ringing circuit from the trunkline, and a third electromagnetic mechanism controlled by the cordcircuit operator and adapted upon actuation to change the circuit forthe second electromagnetic mechanism to cause actuation thereof toconnect the ringing circuit with the trunk line whereby ringing currentwill pass through the telephone line and substation connected with thetrunk circuit.

8. In a telephone exchange system, the combination with a trunk line forconnection with telephone lines leading to sub stations to be called, ofa cord circuit for connecting said trunk line with telephone linesleading to calling substations, a source of ringing current associatedwith the trunk circuit, electromagnetic mechanism actuated uponconnection of the cord circuit with the trunk line to continue thecircuit from the ringing source to the trunk circuit, a secondelectromagnetic mechanism controlling the connection of said ringingcircuit with the trunk circuit and actuated upon connection of the cordcircuit with the trunk line to disconnect the ringing circuit from thetrunk line, a third electromagnetic mechanism controlled by the cordcircuit operator and adapted upon actuation to change the circuit forthe second electromagnetic mechanism to cause actuation thereof toconnect the ringing circuit with the trunk line whereby ringing currentwill pass through the telephone line and substation connected with thetrunk circuit, and a fourth electromagnetic mechanism controlling saidthird electromagnetic mechanism to restore the second electromagneticmechanism circuit to its normal condition whereby the source of ringingcurrent is again disconnected from the trunk line.

9. In a telephone exchange system, the combination with a trunk line forconnection with telephone lines leading to substations to be called, ofa cord circuit for connecting said trunk line with telephone linesleading to calling substations, a source of ringing current associatedwith the trunk circuit, electromagnetic mechanism controlling theconnection of said source with the trunk line and controlled by theconnection of the cord circuit with the trunk line, a relay associatedwith the trunk circuit and responsive to alternating current, said relaycontrolling said electromagnetic mechanism, a source of alternatingcurrent for the cord circuit adapted upon connection of said cordcircuit with the trunk line to be actuated to send current through thetrunk line and relay connected therewith, additional electromagneticmechanism associated with the trunk circuit and adapted to maintainencrgization of the relay, encrgization of said relay causing actuationof the electromagnetic mechanism to connect the ringing source with thetrunk circuit and connected line, said additional electromagnetic meansbeing adapted upon actuation of substation apparatus in response tosignaling current to cause deenergization of the relay whereby the firstelectromagnetic mechanism may disconnect the signaling current from thetrunk circuit.

10. In a telephone exchange system, the combination with a trunk circuitfor connection with a called line, of a cord circuit for connecting saidtrunk circuit with calling lines, ringing current apparatus associatedwith the trunk circuit, electromagnetic mechanism for connecting saidringing current mechanism with the trunk circuit and connected line, arelay connected with the trunk line for controlling the circuit throughsaid electromagnetic mechanism, a generator associated with the cordcircuit, a winding for said relay responsive to current from saidgenerator, a local energizing circuit for said relay for maintainingenergization thereof after initial energization thereof by thealternating current, cnergization of said relay causing actuation of theelectromagnetic mechanism to connect the ringing circuit with the trunkcircuit and connected line, and additional electromagnetic mechanismcontrolling said local circuit, said additional electrtnnagneticmechanism being controlled by apparatus at the called substation andadapted upon actuation of said apparatus in response to signalingcurrent to break the local circuit whereby said relay becomesdeenergized and said first electromagnetic mechanism actuated todisconnect the ringing circuit from the trunk circuit.

11. In a telephone exchange system, the combination with a trunk linefor connecting with lines leading to the substations to be called, of acord circuit for connecting said trunk line with telephone lines leadingto calling substations, a source of ringing current associated with thetrunk circuit,

electromagnetic mechanism controlling the 1 ing source with the trunkcircuit, a local diconnection of said source With the trunk circuit andline connected therewith, a relay associated with the trunk circuit forcontrolling the circuit for said electromagnetic mechanism, a circuitfor said relay controlled by the cord circuit operator for causingactuation of said relay to control the electromagnetic mechanism, toconnect the source of ringing current with the trunk circuit and lineconnected therewith, and a second circuit for said relay controlled bythe connected substation on the called line, actuation of substationapparatus in response to signaling current causing said relay to beinfluenced to control the electromagnetic mechanism to disconnect thesignaling current source from the trunk circuit.

12. In a telephone exchange system, the combination with a trunk circuitfor connection with lines leading to substations to be called, of a cordcircuit for connecting said trunk circuit with lines leading to callingsubstations, a source of ringing current associated with the trunkcircuit, electromagnetic mechanism for connecting said source with thetrunk circuit and connected line, a relay for controlling the circuitthrough said electromagnetic mechanism, an alternating currentenergizing circuit for said relay controlled by the cord circuitoperator to initially energize the relay to cause operation of theelectromagnetic mechanism to connect the ringing current with the trunkcircuit, a direct current energizing circuit for the relay closed uponenergization thereof by the alternating current circuit to maintainenergization of the relay upon opening of the alternating currentcircuit, said direct current circuit being controlled from the calledsubstation, actuation of substation apparatus in response to signal ingcurrent causing opening of the direct current circuit, whereupon saidrelay becomes deenergized and the electromagnetic mechanism operated todisconnect the ringing source from the trunk circuit.

13. In a telephone central exchange system, the combination with a trunkline for connection with lines leading to substations to be called, of acord circuit for connecting said trunk line with telephone lines leadingto calling substations, a source of ringing current associated with thetrunk circuit, electromagnetic mechanism for cont-rolling the connectionof said ringing source with the trunk circuit and line connectedtherewith, a relay for controlling the circuit through saidelectromagnetic mechanism, an alternating current energizing circuit forsaid relay controlled by the cord circuit operator and adapted toinitially energize the relay whereby the electromagnetic mechanism iscontrolled to connect the ringrect current energizing circuit for saidrelay for maintaining energization thereof after opening of thealternating current energizing circuit, additional electromagneticmechanism controlling said local circuit, said ad ditionalelectromagnetic mechanism being controlled from the called substation,actuation of apparatus at the substation responsive to signaling currentcausing said additional electromagnetic mechanism to open the localcircuit whereby said relay becomes deenergized and the electromagneticmechanism controlled to disconnect the signaling source from the trunkcircuit.

14. In a telephone exchange system, the combination with a trunk linefor connecting with lines leading to substations to be called, of a cordcircuit for connecting said trunk line with telephone lines leading tocalling substations, a source of ringing current associated with thetrunk circuit, electromagnetic mechanism controlling the connection ofsaid source with the trunk circuit and the line connected therewith, acircuit for said electromagnetic mechanism closed upon connection ofsaid cord circuit with the trunk circuit whereby said electromagneticmechanism is energized to disconnect the ringing source from the trunkcircuit, a relay controlling the circuit for said electromagneticmechanism, a source of current for the cord circuit, switching meanscontrolled by the cord circuit operator for connecting said source ofcurrent to send current through said relay whereby said relay isactuated to open the circuit for the elec tromagnetic mechanism, saidmechanism ,upon deenergization causing connection of the signalingsource with the trunk circuit and line to be called.

15. In a telephone exchange system, the combination with a trunk circuitfor connection with telephone lines to be called, of a cord circuit forconnecting said trunk circuit with calling lines, a source of signalingcurrent associated with the trunk circuit, electromagnetic mechanismcontrolling the connection of said source with the trunk circuit, acircuit for said electromagnetic mechanism closed upon connection of thecord circuit with the trunk line, whereby said mechanism becomesenergized to disconnect the source of calling current from the trunkline, a relay controlling the circuit through said electromagneticmechanism, an alternating current energizing circuit for said relayincluding part of the trunk circuit and part of the cord circuit andcontrolled by the cord circuit operator, said circuit upon clo surecausing initial energization of the relay to control the circuit for theelectromagnetic mechanism to cause deenergization thereof and connectionof the signaling source with the trunk circuit, a local direct currentenergizing circuit for the relay, energization of the relay by thealternating current circuit causing closure of the direct currentenergizing circuit whereby energization of said relay is maintained,additional electromag netic mechanism controlling said local circuit,and a circuit for said additional electromagnetic mechanism includingapparatus at the called substation, actuation of said apparatus causingclosure of the circuit through the additional electromagnetic mechanismwhereby the local circuit is opened and the relay denergized,

16. In a telephone exchange system, the combination of a trunk circuitat a main exchange adapted for connection with lines leading tosubstations to be called, of a cord circuit at a subexchange forconnecting said trunk line with lines leading to calling sub stations, asource of ringing current at the main exchange, means controlled by thesubexchange operator for primarily establishing connection between thesource of ringing current and the trunk line whereby ringing currentpasses from the trunk line through the line to be called connected withthe trunk line, automatic means for maintaining the flow of callingcurrent to the called substation, and electromagnetic means forautomatically causing disconnection of the source of ringing currentfrom the trunk circuit when the called subscriber answers, the circuitfor said electromagnetic means being normally open at the main exchangeuntil closed by the actuation of substation apparatus in answer to thecall.

17 In a telephone exchange system, the combination with a trunk circuitat a main exchange adapted for connection with lines leading tosubstations to be called, of a cord circuit at a subexchange forconnecting said trunk line with lines leading to calling substations, asource of calling current at the main exchange, a source of directcurrent at the main exchange, means controlled by the subexchangeoperator for alternately connecting said ringing current source and thedirect current source With the trunk circuit whereby when said trunkcircuit is connected with a line to be called calling current and directcurrent Will alternately pass through the line and substation to becalled, and means controlled by apparatus at the called substation forcausing disconnection of the ringing and direct currents from the trunkcircuit.

18. In a telephone exchange system, the combination with a trunk circuitat a main exchange adapted for connection with lines leading tosubstations to be called, of a cord circuit at a subexchange forconnecting said trunk line with lines leading to calling substations, asource of calling current at the main exchange, a source of directcurrent at the main exchange, means controlled by the subexchangeoperator for alternately connecting said ringing current source and thedirect current source with the trunk circuit whereby when said trunkcircuitis con nected with a line to be called calling current and directcurrent will alternately pass through the line and substation to becalled, and means controlled by apparatus at the called substation andresponsive only to direct current flow for causing disconnection of theringing and direct currents from the trunk line.

19. In a telephone exchange system, the combination with a trunk circuitat a main exchange adapted for connection with lines leading tosubstations to be called, of a cord circuit at a subexchange forconnecting said trunk line with lines leading to calling substations, asource of ringing current at the main exchange, a source of directcurrent at the main exchange, means at the main exchange controlled bythe subexchange operator for closing circuits leading ringing currentand directcurrent to the trunk circuit, additional electromagneticmechanism at the main exchange controlled by the subexchange operatorfor connecting said ringing current and direct current circuits with thetrunk circuit whereby ringing and direct currents will flow into theline and substation to be called when the trunk circuit is connectedwith the line, means for causing the ringing current and direct currentto flow alternately, and additional electromag netic means at the mainexchange controlled by apparatus at the called substation and responsiveonly to the direct current flow to cause disconnection of both thedirect and calling current circuits from the trunk cir cuit uponactuation of substation apparatus in response to the call.

20. In a telephone exchange system, the combination with a trunk circuitat a main exchange adapted for connection With lines leading tosubstations to be called, of a cord circuit at a subexchange forconnecting said trunk line with lines leading to calling substations, asource of ringing current at the main exchange, a source of directcurrent at the main exchange, electromagnetic mechanism at the mainexchange for closing circuits for leading direct and ringing current tothe trunk circuit, said electromagnetic mechanism being controlled bythe subexchange operator, a second electromagnetic mechanism at the mainexchange also controlled by the subexchange operator for connecting theringing and direct current circuits with the trunk circuit wherebyringing and direct currents will flow into the line and substation to becalled when the trunk circuit is connected with the line, a thirdelectromagnetic mechanism associated with disconnect the ringing anddirect current both the ringing and direct current circuits circuitsfrom the trunk line. 10 but responsive only to direct current said InWitness whereof, I hereunto subscribe third electromagnetic mechanismbeing conmy name this 20th day of April A. 1)., 1907. trolled from thesubstation and operated CHARLES E. HAGUE. upon actuation of substationapparatus in lVitnesses:

response to the call to affect the circuit of ALBERT C. BELL,

the second electromagnetic mechanism to ARTHUR R. KAHL.

